The invention relates to a stretching device for stretching an apex filler strip prior to application to a bead and an apex handling system comprising said stretching device.
DE 28 03 460 A1 discloses a drum with a plurality of pressure rollers for guiding a profile strip in a loop around the drum. The profile strip is supported on the drum with in a substantially parallel orientation to the rotation axis of the drum, in which the tip of the profile strip is not located radially outside the base portion thereof. Also, the profile strip is maintained constantly in said parallel orientation at a constant angle to the rotation axis of the drum directly prior to, during and directly after the loop. Stretching of the tip of the profile strip does therefore not occur.
WO 00/23262 A1 discloses an apparatus for forming an elastomeric extrusion into a bead apex filler and for applying the same to an annular bead to form a bead/apex subassembly for use in the construction of a pneumatic tire. The apex filler is formed from a triangular shaped extrusion that is wrapped around a rotating mandrel in an upright position with the tip of the apex filler extending radially outward. A helical former disposed around the mandrel on the outside of the apex filler forces the apex filler to move in a helical path as it traverses the mandrel with a constant orientation with respect to the rotation axis of the mandrel. The radially outer tip travels a longer circumference than the base portion of the apex filler, and is stretched as a result thereof. The extrusion is cooled while on the mandrel to cure the elastomeric material of the apex filler. As the extrusion is removed from the mandrel, the extrusion is relieved of compressive or tensile stresses. Then, the apex filler is wrapped around the outer periphery of the bead to form a bead/apex filler subassembly. The rotating mandrel consumes a lot of space on the factory floor. Furthermore, as the extrusion is forced into a helical path right after extrusion, it is no longer possible to linearly transport the apex filler, e.g. in a festooner, without again introducing stresses into the apex filler.
U.S. Pat. No. 5,100,497 A discloses an apparatus for forming an apex filler without the introduction of stresses at the outer edge of the apex filler. The elastomeric strip is supplied to a chuck in an upright position, with the tip of the apex filler at a radially outer position with respect to the chuck. A pair of opposed, forming rollers present a nip which is arranged to frictionally engage the elastomeric strip at the tip. The interaction between the elastomeric strip and the nip effects rotary motion of the elastomeric strip and increases the circumferential length of the elastomeric strip proportionally to the radial distance outwardly from the base thereof. An apex filler applying apparatus subsequently applies the apex filler onto the radially outer surface of a bead ring sub-assembly arranged on the chuck. It is observed that, in practice, the frictional elongation at the nip between the forming rollers may not be sufficient to achieve the required elongation.
It is an object of the present invention to provide an alternative stretching device for stretching an apex filler strip prior to application to a bead and an alternative apex handling system comprising said stretching device.